What is ICU?

ICU is a mature, widely used set of C/C++ and Java libraries providing Unicode and Globalization support for software applications. ICU is widely portable and gives applications the same results on all platforms and between C/C++ and Java software.

ICU is released under a nonrestrictive open source license that is suitable for use with both commercial software and with other open source or free software.

Here are a few highlights of the services provided by ICU:

Code Page Conversion: Convert text data to or from Unicode and nearly any other character set or encoding. ICU's conversion tables are based on charset data collected by IBM over the course of many decades, and is the most complete available anywhere.

Collation: Compare strings according to the conventions and standards of a particular language, region or country. ICU's collation is based on the Unicode Collation Algorithm plus locale-specific comparison rules from the Common Locale Data Repository, a comprehensive source for this type of data.

Formatting: Format numbers, dates, times and currency amounts according the conventions of a chosen locale. This includes translating month and day names into the selected language, choosing appropriate abbreviations, ordering fields correctly, etc. This data also comes from the Common Locale Data Repository.

Time Calculations: Multiple types of calendars are provided beyond the traditional Gregorian calendar. A thorough set of timezone calculation APIs are provided.

Unicode Support: ICU closely tracks the Unicode standard, providing easy access to all of the many Unicode character properties, Unicode Normalization, Case Folding and other fundamental operations as specified by the Unicode Standard.

Why Unicode?

Unicode (and the parallel ISO 10646 standard) defines the character set necessary for efficiently processing text in any language and for maintaining text data integrity. In addition to global character coverage, the Unicode standard is unique among character set standards because it also defines data and algorithms for efficient and consistent text processing. This simplifies high-level processing and ensures that all conformant software produces the same results. The widespread adoption of Unicode over the last decade made text data truly portable and formed a cornerstone of the Internet.

Globalized software, based on Unicode, maximizes market reach and minimizes cost. Globalized software is built and installed once and yet handles text for and from users worldwide and accomodates their cultural conventions. It minimizes cost by eliminating per-language builds, installations, and maintenance updates.

Why ICU4C?

The C and C++ languages and many operating system environments do not provide full support for Unicode and standards-compliant text handling services. Even though some platforms do provide good Unicode text handling services, portable application code can not make use of them. The ICU4C libraries fills in this gap. ICU4C provides an open, flexible, portable foundation for applications to use for their software globalization requirements. ICU4C closely tracks industry standards, including Unicode and CLDR (Common Locale Data Repository).

Why ICU4J?

Java provides a very strong foundation for global programs, and IBM and the ICU team played a key role in providing globalization technology into Sun's Java. But because of its long release schedule, Java cannot always keep up-to-date with evolving standards. The ICU team continues to extend Java's Unicode and internationalization support, focusing on improving performance, keeping current with the Unicode standard, and providing richer APIs, while remaining as compatible as possible with the original Java text and internationalization API design.

ICU4JNI

New versions of ICU4JNI are no longer being created. If you need the functionality of ICU4JNI, you should consider migrating to ICU4J.

Who Uses ICU?

The following is a list of products, companies and organizations reported to be using ICU. If you have any feedback on this list (corrections, additions, or details), please contact us (on icu-support).